This invention relates to contact lenses and in particular to ways of increasing the flow of oxygen and nutrient laden tears through contact lenses to the surface of a wearer""s cornea.
Hard contact lenses have the advantages of longevity, biocompatability, strength, durability, wettability and the ability to compensate for some types of astigmatism. However, conventional hard contact lenses also act as a barrier to reduce the flow of oxygen and nutrients to the corneal surface, which may lead to oedema and other undesirable effects. Soft contact lenses have been developed which have a higher oxygen permeability than hard contact lenses and thereby reduce the incidence of oedema and similar effects. However, even oxygen permeable contact lenses reduce the flow of oxygen and nutrient laden tears to the cornea. This reduced flow of tears can result in the accumulation of metabolic products from corneal cells behind the lens, growth of bacteria behind the lens, and general wearer discomfort.
One method previously disclosed to partially alleviate these problems has been to xe2x80x9cfenestratexe2x80x9d the contact lenses by creating holes passing completely through the lenses to allow bulk tear flow and the transfer of dissolved oxygen through the lenses and to the eye surface. Various techniques have been proposed for the fenestration of contact lenses. For example, one system (see e.g., U.S. Pat. No. 3,227,855) uses a spark to locally burn a small hole through the lens. Others (see e.g., U.S. Pat. Nos. 3,833,786 and 3,971,910) describe laser based systems in which a concentrated beam is used to burn through the lens to produce the holes. Still other systems use drills to mechanically bore holes through the lens (see e.g., U.S. Pat. No. 6,101,219)
Conventional fenestrated contact lenses have holes intended to provide bi-directional diffusion of oxygen and/or flow of tears. However, by their passive and non-directional nature, these contact lenses have a less than optimal tear flow which can potentially result in low tear and oxygen flow to certain areas of the cornea. Their fenestrations also have a tendency to clog resulting in impaired tear flow. There is clearly a need for a fenestrated contact lens having an improved tear flow to improve corneal health and reduce the risk of corneal damage due to oxygen or nutrient starvation of the corneal cells.
Accordingly, it is an object of the present invention to provide a fenestrated contact lens having an increased oxygen and tear flow to the corneal surface.
It is another object of the present invention to provide a fenestrated contact lens that will direct tear flow in a desired pattern to optimize tear flow to the cornea.
It is yet another object of the present invention to provide a method for producing fenestrated contact lenses having increased tear flow characteristics.
Other objects, aspects, and advantages of the present invention will be apparent to those skilled in the art from a reading of the following detailed disclosure of the invention.
The above objectives are accomplished according to the present invention by providing a fenestrated contact lens having increased tear flow. The fenestrated contact lens includes a lens body adapted for placement adjacent a surface of an eye which has an inner surface and an outer surface. The lens body has a first plurality of fenestrations extending therethrough which are biased to direct a flow of tear fluid from a first location between the surface of the wearer""s eye and the inner surface of said contact lens to a second location adjacent the outer surface of the contact lens. The lens body also includes a second plurality of fenestrations extending therethrough, which are biased to direct a flow of tear fluid from a third location adjacent the outer surface of the contact lens to a fourth location between the surface of the eye and the inner surface of said contact lens.